Bypass or wastegate valves are provided for use with boosted engines, such as by turbocharging or supercharging, to prevent overboosting the engine. In one configuration, the wastegate valve is designed to release pressurized exhaust gasses from an exhaust manifold upstream of the high pressure turbine of a turbocharger when the exhaust gas pressure exceeds a predetermined pressure. Alternately, the wastegate valve can release pressurized intake air from an intake manifold when the intake air pressure exceeds a predetermined pressure. Regardless of the point of release, the wastegate valve opens to reduce boost pressure below a predetermined pressure, at which point the wastegate valve then closes.
Typically, the wastegate valve includes a piston movable within a housing. Pressurized manifold gasses are communicated to a side of the piston to actuate the piston between first and second positions. A diaphragm is provided between the movable piston and housing to seal across the piston. Because the diaphragm must flex each time the piston moves, the diaphragm must be able to withstand tearing, for example, due to fatigue of the diaphragm material. Should the diaphragm tear, the pressurized manifold gasses will vent to atmosphere and engine performance will be reduced. In addition to withstanding continued cycling, the diaphragm must be able to withstand the high pressure and high temperature environment common to wastegate valves, for example, in an exhaust gas environment.
The present invention is directed to providing an improved bypass or wastegate valve and, in particular, a wastegate valve that reduces loading of the diaphragm during cyclical operation.